Activated carbon can be used for adsorption purposes, such as the extraction of gases or vapors from products, for adsorption of liquids and for solvent recovery in various applications. One process used in producing highly active gas adsorbent carbon consists of charring carbonaceous material, such as coconut shells, by application of heat and the further treatment of the carbon so produced with an oxidizing agent such as steam which slowly oxidizes the carbon.
U.S. Pat. No. 1,694,040 discloses a process for making dense strong activated charcoal by impregnating nut cellulose with a dehydrating agent, such as phosphoric acid or zinc chloride, heating the mixture to a temperature not materially below 350.degree. C., leaching out the soluble components and then reheating the resulting carbon in an oxidizing atmosphere.
U.S. Pat. No. 1,819,165 discloses a process for producing highly active gas adsorbent carbon by impregnating carbonaceous material with phosphoric acid, then calcining said impregnated material in the absence of oxygen and then submitting the calcined product to controlled partial oxidation at temperature above 700.degree. C.
U.S. Pat. No. 3,305,314 discloses a process for producing permanently dehydrated heat treated material from a cellulosic textile material which comprises subjecting the cellulosic material to a controlled partial and selective decomposition of the cellulosic molecule by immersing the cellulosic material in an acid solution to wet the material therewith, removing the wet material from the solution, drying the material to remove the solvent therefrom and heat treating the dried material in an oxidizing atmosphere whereby decomposition involves a rupture of the carbon-oxygen and carbon-hydrogen bonds and the evolution of water, but falling just short of the scission of the main cellulose molecule, through the rupture of the carbon-carbon bonds with the evolution of hydrogen.
U.S. Pat. No. 5,102,855 discloses a process for producing activated carbon, preferably high surface area activated carbon, from inexpensive cellulosic precursor with the activating agent, such as phosphoric acid, followed by carbonization in the inert atmosphere at an elevated temperature to produce activated carbon. The activated carbon can be further activated to increase its surface area by heating it in an oxidizing atmosphere at an elevated temperature to yield activated carbon having a surface area of at least 1000 m.sup.2 /g.
A report of the Ontario Ministry of Transportation and Communications AF-87-02-March 1987 "The Development and Performance Testing of Adsorbent Carbon for the Storage of Compressed Natural Gas"--S. S. Barton, J. R. Dacey, M. J. B. Evans, J. A. Holland, D. F. Quinn, describes work in which fluorine treatment of activated carbons was carried out to determine whether the adsorption of methane could be increased. Fluorination was carried out on Saran carbon and on AX-21 Amoco-type carbon to varying degrees. The fluorinated carbons produced were characterized as to surface area and micropore volume and investigated for methane uptake at 25.degree. C. It was reported that every sample produced showed a substantial reduction in surface area and micropore volume and adsorbed considerably less methane than the original carbon. It was further reported that fluorination of carbons was not considered to be a worthwhile venture.
Active carbon has been used extensively in gas and vapor adsorption devices and is also well suited for the storage of gases such as methane.
It is an object of the present invention to provide a relatively low cost process for treating high surface area activated carbons by halogenation with chlorine, bromine, iodine or by sulfonation with sulfuric acid, fuming sulfuric acid, sulfur trioxide to produce a material having increased storage capacity for gases such as methane.
It is another object of the present invention to provide activated carbons, preferably high surface area activated carbons, that can be utilized in storage containers to more efficiently store gases such as methane, hydrogen and natural gas.
It is another object of the present invention to provide a process for treating high surface area activated carbon to increase its gas storage capacity that is cost effective to produce and easy to practice.